The present invention relates to a lane assistance system for sensing rapidly approaching vehicles from the rear of a vehicle to avoid inopportune lane changes.
Today, rear radar sensors are used for functions, such as blind-spot detection, rear cross traffic alert and closing vehicle warning. For closing or rearwardly approaching vehicle warning functions, systems must meet the ISO17387 norm, which requires that vehicles approaching at a velocity that is 20 meters/second (45 miles per hour (mph)/72 kilometers per hour (kph)) faster than the velocity of a host vehicle, result in a warning for the host vehicle. The warning must occur 3.5 seconds before the closing rearwardly approaching vehicle overtakes the host vehicle.
For all variants of automated driving which allow lane changes, it is important to identify if a subject vehicle on a neighboring lane is approaching extremely quickly, such that a lane change that could be potentially dangerous is not performed by the host vehicle. Unfortunately, today's systems, which are designed to meet a 3.5 second warning of a vehicle approaching a host vehicle from the rear at a relative velocity of 20 m/sec., typically cannot accurately sense a large enough distance rearwardly. Thus, the arrangement is not suitable for autonomous driving applications, as the system cannot provide the information fast enough for vehicles approaching extremely fast.
Some high relative velocity difference scenarios addressed herein are as follows.
On highways, e.g. German Autobahn for example, it is common on certain stretches that cars travelling at 250 kph overtake vehicles travelling at 80 kph. A common accident source is an operator driving a vehicle that is changing lanes behind trucks travelling at 80 kph to pass, not realizing that vehicles on the neighboring lane are approaching very quickly. Although this situation is not typical in some countries, there are additional situations when people speed considerably that need to be considered.
In highway traffic jam situations, occasionally a host vehicle is in a lane travelling slowly (e.g. 10 kph), but vehicles in a neighboring lane are travelling near the speed limit (e.g. 130 kph in many countries).
In city/city-expressway/country-road situations, vehicles in different lanes typically travel at different speeds. Lane changes and lane mergers by a host vehicle travelling at very low speeds to lanes where higher speeds are allowed (e.g. 100 kph) are also common, such that autonomous driving must be able to perform under such conditions.
In current implementations of radar sensing units, the radar sensing unit typically searches for peaks in the received spectrum, and translates the peaks into a measured distance and velocity, wherein high power was received off of reflections of objects. At this data point, angles of the objects with respect to the host vehicle orientation are also calculated.
However, when the angles of objects/vehicles relative to the host vehicle are not determinable or very uncertain, the measurements get rejected. Thus, the position of the approaching object is unknown and no action can be taken.
In other instances, values for the angles of objects relative to the host vehicle are obtained, but due to the large distance of the object from the host vehicle, the objects have a distribution that covers multiple lanes, such that there is no possibility of associating the detected vehicle to a specific lane. This event leads to missed or false interpretations of what lane the fast approaching object is in.
The objective of the invention is to identify when a vehicle is approaching extremely quickly from the rear of a host vehicle at a high relative velocity, such that a lane change by the host vehicle that may potentially be dangerous can be prevented, even when the specific lane of the closing rearwardly approaching vehicle is not certain.